Abstract

Studies on the epidemiology of Canine Babesiosis in Minas Gerais, Brazil.
During two stays between April 2004 and February 2005, one in the dry season and the other during the rainy season, a total of 552 samples from 385 dogs (samples from 167 dogs were collected twice) from three different regions (Carrancas,
Carlos Chagas and Igarapé) in Minas Gerais, Brazil were collected. While the first collection only included samples from dogs living in rural areas the second collection gathered repeat samples from the dogs from the first collection as well as samples from dogs from the particular urban areas. Blood was taken from each dog and blood smears were prepared. The blood smears were microscopically analysed and the DNA, extracted from the blood, was used for Real-Time PCR analysis of infections with Babesia canis vogeli or other piroplasms. A conventional PCR for the detection of Babesia sp. was carried out. In addition an indirect immunfluorescent-antibody-test, specific for Babesia canis vogeli, was performed with all samples.
The analysis of samples from the first collection period resulted in a percentage of prevalence of 10,3 % in the Real-Time PCR and 30,0 % in the indirect immunfluorescent-antibody-test. The second collection period showed a prevalence of 8,2 % in the Real-Time PCR and 21,7 % in the indirect immunfluorescent-antibody-test. No significant difference has been found in the results from the Real-Time PCR and the origin (urban-/rural area) of the dogs in Minas Gerais, in general. However, on examining the three different regions separately, a significant difference in prevalence emerged in Carlos Chagas. In Minas Gerais there was a highly significant difference shown in the results of the indirect immunfluorescent-antibody-test. While Carrancas showed no significance at all, there was a significant difference shown in the results of Carlos Chagas and a highly significant difference shown in Igarapé. Due to the very low sensitivitiy of the microscopically analysation only two from the 552 samples were positive.
With regards to the two different time periods (dry and rainy season) in which samples where collected, no significant differences in the results of the
Real-Time PCR were recorded in Minas Gerais in general or in the various regions in particular. The results of the indirect immunfluorescent-antibody-test did not show any significance in Minas Gerais, generally, or the regions of Carrancas and Carlos Chagas in particular, whereas in Igarapé a significant difference was visible. Comparing the different age groups, a significant difference was detected in the
Real-Time PCR results and a highly significant difference in the results from the indirect immunfluorescent-antibody-test. Concerning the difference in prevalence’s of infections and antibodies based on sex (male/female) the results of the PCR showed no significant difference whereas the difference in seroprevalence was significant. The results of the hematocrit and a comparison with the positivity in the different diagnostical methods revealed no significance for the indirect immunfluorescent-antibody-test and a high significance for the Real-Time PCR. A reason for the differences in prevalences across different age groups, as compared to the results from the Real-Time PCR, could be that puppies are more prone to infections. In the results of the indirect immunfluorescent-antibody-test a higher prevalence in the older age groups points to a certain resistance of those animals after recovering from infections with B. canis vogeli. A likely cause for the differences in prevalence in the results of the Real-Time PCR and the indirect immunfluorescent-antibody-test compared to the origin (rural or urban area) of the dog samples are differences in keeping the dogs as well as a lower occurrence of the vector ticks in the urban areas.